1.2 Ensure that displays are within sight of people of all heights and people sitting in a wheelchair or buggy

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A "display" encompasses anything from a single line LCD display through computer monitors to large public information display boards, such as those used at railway stations to indicate train times. In the latter case, the display comprises the complete PAT, since there are no user-operated parts.

Being "within sight" means that the user's line of sight to the display is unobstructed at a distance and angle that enables the display to be read clearly by someone with 20:20 vision, within the environmental constraints such as ambient lighting (allowing for users with restricted vision is covered in other checkpoints). The display should be within sight from whatever position and orientation the user finds themselves in naturally when using the terminal. This will be different depending on the person's height and whether they are sitting in a wheelchair or motorised buggy.

A display that is positioned for optimal viewing by users of average height may present difficulties for other non-average users. Users who are extremely short, extremely tall, or who sit in a wheelchair will be looking either up or down at the display and from further away. The increased distance may mean that fine text or information is difficult to read. The more acute angle may also affect readability by changing the aspect ratio. Or it may mean that other parts of the terminal get in the way.

A particular problem for people looking upwards at the display is the effect of reflected light. Some terminals, particularly ATMs in the street, are completely unreadable when the sun is shining on them. Someone who is taller can often position their body between a light source such as the sun and the display, making it easier to read.

"Light and reflections are always a problem due to the viewing angle. If you are looking down, your shadow covers the screen. Imagine you are sitting and have to stretch your head to see the screen. Once I withdrew too much money because I couldn't see the screen properly. " - wheelchair user

Line of sight Ensure that there is a clear line of sight to the display from a range of angles. Check for glare on the screen from a range of positions.

Refer to anthropometrical data

Refer to appropriate physical design guidelines or building accessibility guidelines which give minimum and maximum heights. The United Nations have a useful set of anthropometrical data covering ranges of height and reach when standing or sitting in a wheelchair.

Eye height ranges Ensure that users of all heights can see displays. The standing eye height for the largest person (95th percentile) is approx. 1.8m. The standing eye height for the smallest person is approx. 1.35m. Wheelchair users often have eye heights as low as 1.15m.

Reduce glare

Anti-glare displays can help reduce the problem of reflected light. The physical design of the terminal casing can also help by blocking light from reaching the display. However, be aware that anything that obstructs light from reaching the display may also obstruct the user's view.

Increase size

Increasing the size of text or other displayed information can help to make it more readable at an angle.

Consider adjustable or extra displays

In extreme cases, you may consider using height adjustable or rotatable displays or dual-display systems.

Self-test early prototypes

Designers can run simple sight tests on a prototype, simulating short and tall people and wheelchair users by sitting in a chair, standing on a raised area or kneeling down. Whilst this will not be a replacement for proper testing with real users, it will give some insight into what it is like to be viewing the display from the user's perspective and will help reveal any obvious problems before further work is carried out. If standing on something, you should make sure it is sufficiently strong and stable and take care to avoid the possibility of injuries caused by falling off it. Difficult lighting conditions are easily simulated by either using the prototype outside in sunlight or positioning artificial lights appropriately.

Include user data in the design

If you are designing using a CAD package, you may be able to simulate different viewing points before creating a prototype.

Test with real users

During development, you should test the prototype in a realistic situation with real people, particularly people who routinely use wheelchairs or motorised buggies. About user testing